The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A digital map can include patches of color to depict bodies of water, forested areas, ice sheets, etc. In some cases, a color gradient can be introduced to a patch of color to make the contrast between the patch and adjacent graphical elements sharper. For example, a sea can be represented by a shape filled with a constant shade of blue, except that a darker shade of blue near the coastline makes the boundary between water and land more clear. In other words, representations of bodies of water can be stylized.
Patches of color can be provided to client devices as raster (bitmap) images. Further, a server can provide a client device with blurred raster images of map elements for generating certain visual effects, such as a stylized body of water, rather than relying on the client device to perform the blurring operation. This server-side blurring operation reduces bandwidth costs to the client device, because the generation of a blurred region requires source data from raster images larger than the final blurred result (i.e. a pixel in the blurred result gets color contributions from surrounding pixels). In addition, the server-side blurring operation saves the client device from doing the computationally expensive work of generating a blur. However, unlike vector graphics content, bitmap images generally do not scale well. In the example above, naively scaling a stylized representation of a body of water can make the stylized land/water margin too wide or too narrow, depending on whether the image with the stylized gradient was enlarged or reduced.